Stringed instruments in a form of MIDI controllers are well known. For instance, the basic configuration may consist of a guitar (U.S. Pat. Nos. 5,619,003; 5,396,828; 4,630,520, etc.) like device with emulation of the strings and frets (U.S. Pat. Nos. 5,398,585; 5,033,351; etc.)
The fret board of the guitar in electronic version is normally used as a switching device and string vibration picked up by input sensors and processed in order to determine trigger and velocity events for initiating specific note or groups of notes in accordance with minute state of the fingerboard switches. These instruments generally may have electronic micro processing unit/s (CPU), scanning device for determining the position of the finger and synthesizer and/or MIDI compatible output. Some devices include internal amplifier and a speaker that allow to play the instrument without external audio system.
In addition there are well known electric-acoustic guitars which allow to play it in a normal acoustic mode or with external amplifier-speaker system. These guitars do not offer electronic chord creation by depressing just one fret and do not have means for reproducing a sound in electronic mode. It is important to mention that about 90% of first time guitar buyers are giving up their efforts within the first month of practicing because of difficulties associated with playing chords and particularly its fingering.
Stringed instruments with simplified fingering for creation of chords or so-called easy to play guitars are well known from the prior art. One of the earliest attempts to create a simple fingering device for chord creation was a “Guitarola™”—a mechanical device that was to be attached to the guitar neck above the strings. Using just one finger, the player could create a variety of chords predetermined by a mechanical configuration of the device design. This device was generally difficult in use and it offered only limited number of chords to be played. In addition the guitar itself needed to be always properly tuned.
There also electronic guitars known which allow easy fingerings (for instance a U.S. patent application Ser. No. 09/496,040; Okulov et al.) The idea of easy to play instrument lies in providing initial and successful experience in playing guitars and teaching a user the skills necessary for playing a normal instrument. This device comprise a finger position recognition system, strings' sensors, CPU, memory and memorized notes, melody and chord tables and audio output means. Pressing a single finger allow to designate a chord and strumming strings allows to play full chords or to play melody notes depending on a status of the operation of the device.
In order to reduce the loudness of the sound of the strings when used as a triggering device, many of the designs mentioned above have mechanical means for string damping made in a form of soft rubberlike foams or gel contacting strings directly near the bridge. These dampers can significantly reduce the audio output of the vibrating string. The disadvantage of such devices is that having mechanically damped the string, its normal oscillations are distorted and therefore provide no input information from the strings on a status of its vibration after note ON event. That makes playing of such instrument unnatural, especially when note ON or muting is desired. There are technical solutions where the bridge can be disconnected from the sound board (U.S. Ser. No. 09/496,040; Okulov et al.) However the presence of moving parts complicates the overall design of the guitar and is a potential source of buzzes and unreliable behavior during the operation.
There are also devices known from the prior art which are to provide audio signal by means of internal speaker (mostly used in toy guitars and travel type electric guitars.) Because of the limited space and weight considerations, speaker quality normally is severely compromised and its output is unacceptable from the point of view of quality of the sound.
The limitation of these instruments however exists that switching is needed between melody and chord mode which distracts attention of the player and creates delay. Another source of problem is the fact that these instruments use MIDI protocol for note generation and require employment of a synthesizer which create delays in generating note ON-OFF events and determination of velocity of the signal. Still another disadvantage of the prior art instruments is significant weight of the instrument and elevated power drain due to use of conventional speakers.
The prior art also include guitars employing various transducers attached to the sound board and used for sustaining of the signal picked up from the strings, however these devices neither provide creation of the high quality sound through the guitar's own sound board, nor do they provide transducer means employing low power drain vibrating piezoelectric systems.
The difference between a guitar as a stringed instrument, for example a piano, in terms of the complexity of note ON-OFF and velocity generation process is that before the piano key hits the mechanism of the hammer or electric switch and the sound is created it is possible to estimate the velocity of the moving key and to apply it to the corresponding generated note before the key provides ON or OFF event. Contrary, in case of guitars, when the string is released by plucking, strumming or hammering by fingers or a pick, the velocity of this given string is not determined yet but the sound is ON already. This is why the note ON event always comes with delay and even the best guitar MIDI instruments provide delays more than 30 ms which are still quite noticeable for experienced player or listener.
There are several methods known from the prior art which include differentiation of the input signal from the strings in order to determine note ON or OFF event (U.S. Pat. Nos. 4,939,471; 5,710,387; 6,091,013). These methods are particularly useful in recognition of the start of the note in case of percussion or plucked musical instruments, in the case of which an envelope curve following function is formed from an audio signal, a comparison variable is formed from a current value of the envelope curve following function and a predecessor value corresponding to an earlier value, and the start of a note is defined at a point in time at which the comparison value exceeds a threshold value. Being analog or digital in its nature these methods however do not teach methods of determination of the velocity of the note simultaneously or within reasonable delay with note ON event or the negative velocity (speed of muting or decaying) when the string is stopped, muted or dumped. In addition the influence of small changes in compared values of the envelope signal provides great amount of false triggering and makes these methods unreliable. Another disadvantage is the fact that these instruments do not teach pitch control techniques which would be a natural and important value necessary to create realistically sounding and easy to play electronic-acoustic guitar.
All of these disadvantages are overcome in present invention.